In recent years, liquid crystal display devices have come to be widely used in smartphones, personal digital assistants (PDAs), tablet computers, satellite navigation systems, etc. In general, a liquid crystal display device comprises a liquid crystal display panel and a surface illumination device which is overlaid on the rear surface of the liquid crystal display panel and illuminates the liquid crystal display panel. An example of the surface illumination device is a backlight unit including a reflective layer, a lightguide plate (lightguide), an optical sheet, a light source such as LEDs, and a rectangular resin frame. The reflective layer, the lightguide plate, and the optical sheet are stacked on each other, and fitted into the resin frame. The peripheries of the reflective layer, the lightguide plate, and the optical sheet are thereby supported and positioned.
Alternatively, there has been proposed a backlight unit in which a resin frame is fitted into a container case made of a metal plate, and further, a reflective layer, a lightguide plate, and an optical sheet are disposed in the cavity of the resin frame.
In recent years, as display areas have increased, there has been a continual demand for the frames of liquid crystal display devices to become ever narrower and the liquid crystal display devices to become ever thinner. However, the above-described backlight unit including the resin frame is approaching the structural limit of the resin frame, and it is hard to meet the demand for further reduction in thickness and further narrowing of the frame.